It is often desirable to hold a tool in close proximity to a vertical, inverted, inclined surface, curved, compound, or tapered surface and to move the tool to various locations on the surface. Some common scenarios include inspecting, cleaning, depainting, or otherwise maintaining the surfaces of airplanes, submarines, storage tanks, high rise buildings, and other similar structures. These surfaces can be inconvenient, difficult or even dangerous, for people to access directly. The difficulty can be increased when these surfaces are curved, compound, or tapered. Accordingly, it has been known to use an apparatus capable of traversing such surfaces and for supporting tools to work on the surfaces. For example, Jeswine, U.S. Pat. No. 6,742,617, discloses a surface clinging unit that includes a plurality of adherence members, in the form of suction cups that are used to adhere to a surface and a safety tether between two robots.
Therefore there is a need for an improved traction device, and especially for a vehicle or robot that utilizes such an improved traction device to cling to and move around on vertical, inverted, or inclined surfaces, and especially on surfaces that are curved, compound, or tapered.